Apparatus for grinding a tungsten electrode for a tig-welding handle

ABSTRACT

An apparatus for grinding a tungsten electrode ( 40 ) for a TIG-welding handle, comprising a grinding arrangement comprising a rotatable grinding wheel and means for rotating the electrode, the apparatus comprising a housing surrounding the grinding device and having an opening ( 31, 31 ′), the free end of the electrode that protrudes from an end portion of the welding handle being insertable into the opening of the housing by means of the welding handle. The opening of the housing wall is directed towards the axis of rotation ( 13 ) of the support ( 12 ) and the grinding rod ( 23 ) is located in the vicinity of the opening ( 31,31 ′) through the wall ( 30 ) of the housing.

The invention relates to an apparatus for grinding a tungsten electrodefor a TIG-welding handle, of the type described in the preamble to claim1.

When performing TIG (Tungsten Inert Gas) welding, which is often usedfor welding stainless steel, the tip of the electrode needs to besharpened from time to time, the operator may sometimes come intocontact with the workpiece with the electrode tip so that the point isdestroyed. The electrode tip is also eroded during operation by theelectric arcs between the tip and the workpiece. It is thus necessary tofrequently sharpen the point to conical shape, for instance, with a topangle of 25 degrees so that the electric arcs are controlled at theelectrode tip.

When the operator considers that the electrode needs sharpening he/sheremoves it from the welding handle and manually grinds the front end ofthe electrode to a sharp point, after which the electrode is replaced inthe welding handle. The dismantling and assembly are time consuming andsometimes difficult since the electrode becomes hot during use.

One object of the invention is therefore to provide a grinding unit thatfacilitates grinding the electrode tip while the electrode remains inthe welding handle.

The known technology is represented by GB 1430041 illustrating a heavywelding unit of TIG type in which the welding electrode is carried by apivotable holder to be swung between a working position and are-grinding position, there being a grinding wheel close by theelectrode tip in the grinding position. The welding unit carries theelectrode via an electrode holder that is rotatably journalled and has arotary motor enabling the electrode to rotate during the grinding.

The invention, however, relates to an apparatus for grinding anelectrode for a manual TIG-welding handle.

The object is achieved by means of the invention.

The invention is defined in the appended independent claim.

Embodiments of the invention are defined in the appended sub-claims.

Basically the invention provides a grinding machine similar to apencil-sharpener, which is placed inside a housing provided with anopening into which the free end of the electrode protruding from thewelding handle can be inserted to correct alignment with the grindingwheel of the unit so that, upon activation, the grinding unit produces asharp conical point on the tip of the electrode when this is insertedthrough the opening in the wall of the housing. A curtain of light or apressure-sensitive member, for instance, may be arranged to sense thatthe electrode tip is inserted through the opening into the housing.

The grinding unit may comprise a support which is rotationally driven bya motor around an axis directed to the electrode tip which is insertedinto the opening of the housing wall. On the support is a motor whoseshaft carries a grinding rod that shapes the electrode tip. The motoraxis of the grinding rod may intersect the axis of rotation of thesupport and form an acute angle therewith corresponding to half thedesired top angle for the electrode tip. The motor may be carried by thesupport via a hinge allowing it to be swung in an axial plane to theaxis of rotation of the support. The motor can thus swing towards anouter end position defining the desired shape of the electrode tip. Themotor may also be pre-stressed to this shoulder by the compressionspring that permits the motor to swing to an obtuse angle to the axis ofrotation of the support and to give way when the electrode is insertedinto the housing to make contact with the grinding wheel. Duringgrinding the grinding wheel rotates, generally at a speed considerablyhigher than the speed of rotation of the support.

In embodiments the opening may comprise a guide for the end portion ofthe welding handle from which the electrode protrudes. The end portionof the welding handle is generally in the form of a section of ductingwhich carries inert gas to the welding area. The wall of the housing maythen provide a guide for this portion of the handle so that theelectrode is directed substantially coaxially to the axis of rotation ofthe support. The opening may possibly include a shoulder forming anaxial stop for the end of the handle part from which the electrodeprotrudes.

In preparation for grinding the electrode tip the operator may possiblyfirst adjust the length of the electrode protruding from the end of thewelding handle.

The invention will be described in the following by way of example withreference to the accompanying drawings.

FIG. 1 shows schematically a section through an apparatus in accordancewith the invention.

FIG. 2 shows another embodiment of the opening of the housing forreceiving an end portion of a TIG-welding handle, from which the weldingelectrode protrudes.

FIG. 1 shows an apparatus housing 1 containing a motor whose out-goingshaft 11 carries a support 12 rotatable about an axis 13. A grinding-rodmotor 20 is pivotably journalled by a bearing on support 12 foroscillation in a plane containing the axis 13. The grinding-rod motorhas an out-going shaft 22 carrying a grinding rod 23 for rotation aboutan axis 24. The support 12 is shown to have a shoulder 14 towards whichthe grinding-rod motor 20 is swung out by a compression spring 15 sothat the axis 24 intersects and forms an angle α with the axis 13 whenthe grinding rod 23 is in proximity to a wall 30 of the housing wall 30and an opening 31 therein, which is directed towards the axis 13. Theconfiguration is such that a straight electrode 40 inserted through theopening 31 encounters the envelope surface of the grinding rod 23 in thevicinity of the free end of the rod 23 close to the wall 30 so that,when the electrode 40 is inserted through the opening 30 it can swingthe motor 20 about its bearing 21 against the action of the compressionspring 15. The shoulder 14 is shown adjustable in order to define anoptional top angle for the electrode tip. The shoulder 14 may be formedby the end of a set screw fitted on the support 12, for instance, in athreaded opening therein.

The electrode 40 is normally held centred in a tubular end piece 42forming an end portion of a TIG-welding handle for manual welding.

A light curtain in the form of an emitter 50 and a sensor 51 senses thatthe tip of the electrode 40 has entered the housing 1, and thus startsthe motors 10, 20, whereupon the motor 20 usually rotates atconsiderably higher speed than the motor 10 while grinding a point atthe end of the electrode 40.

In preparation for the grinding operation the operator can first adjustthe welding handle so that the electrode 40 is pushed sufficiently farfrom the end section 42. FIG. 2 shows an alternative embodiment in whichthe opening 31′ is designed to form a guide for the end portion 42.Cooperation between the opening 31′ and the outer surface of the tubularpart 42 thus establishes a coaxial alignment of the electrode 40 to theaxis 13. The opening 31′ may possibly be provided with a shoulder 32cooperating with the front end of the portion 42 so that, after grindingin the grinding unit, the electrode 40 is protruded a predetermineddistance from the front end of part 42 of the welding handle.

It is also clear from FIG. 1 that an evacuating pipe 2 is connectedthrough the wall 30 of the apparatus housing, in order to evacuate dustand gases from the housing 1. The pipe 2 is connected to a suctionsource and preferably contains filter means (not shown).

1. An apparatus for grinding a tungsten electrode (40) for a TIG-weldinghandle, comprising a grinding wheel (23) rotatable about a first axis(24) and a support (12) carrying the grinding wheel and being rotatableabout a second axis (13), characterised in that the apparatus comprisesa housing surrounding the grinding device and having an opening (31,31′), the free end of the electrode that protrudes from an end portionof the welding handle being insertable into the opening of the housingby means of the welding handle, in that the opening of the housing wallis aligned with the axis of rotation (13) of the support (12) and inthat the grinding rod (23) is located in the vicinity of the opening(31, 31′) through the wall (30) of the housing to form a generatrix tothe desired pointed shape for the free end of the electrode.
 2. Anapparatus as claimed in claim 1, characterised in that the opening (31)through the wall of the housing has a diameter corresponding to thediameter of the electrode (40).
 3. An apparatus as claimed in claim 2,characterised in that the opening (31) is arranged to direct theelectrode (40) to coaxial alignment with the axis of rotation of thesupport.
 4. An apparatus as claimed in claim 1, characterised in thatthe opening has a part (31′) that is arranged guidingly to receive theend portion (42) of the welding handle (44), from which the electrode(40) protrudes.
 5. An apparatus as claimed claim 4, characterised inthat a stop shoulder (32) is arranged at the guiding opening for the endportion (42) of the handle (44).
 6. An apparatus as claimed in claim 2,characterised in that the opening has a part (31′) that is arrangedguidingly to receive the end portion (42) of the welding handle (44),from which the electrode (40) protrudes.
 7. An apparatus as claimed inclaim 3, characterised in that the opening has a part (31′) that isarranged guidingly to receive the end portion (42) of the welding handle(44), from which the electrode (40) protrudes.